Democrats must defend a bigger set of contested races than Republicans.

Story Highlights

Endangered Democratic incumbents in North Carolina and Louisiana outraise their Republican rivals

Republicans in other key states, such Arkansas and Michigan, gain ground in fundraising wars

WASHINGTON — A dozen Democratic candidates in key Senate races collected $1 million or more for their campaigns in the final months of 2013 — as their party fights to retain control of the chamber in November's midterm elections.

Republicans, however, are gaining ground in several crucial contests, including Arkansas, where Rep. Tom Cotton's $1.2 million haul gave the Republican an edge over two-term Democratic Sen. Mark Pryor, one of the Senate's most endangered incumbents.

In Michigan, where both parties are battling over an open Democratic seat, Republican former secretary of State Terri Lynn Land raised more than $1 million and added $600,000 of her own money to her campaign coffers during the fourth quarter of the year to surpass Democrat Rep. Gary Peters, who brought in $1 million.

The political parties are in an all-out war for the Senate, where Republicans have their strongest chance in years of winning the majority. GOP leaders need a net gain of six seats to take control of the chamber and hope to capitalize on President Obama's low approval ratings and the rocky implementation of his signature health care law to sway voters in their favor.

"Whether it's Obamacare or ... growing the economy and creating jobs, voters feel deceived and taken advantage of by their Democratic senators and will vote to replace them with competent and credible alternatives," Brad Dayspring, a spokesman for the National Republican Senatorial Committee, said in a statement.

Democratic incumbents face particularly dangerous terrain in four Republican-leaning states — Arkansas, Alaska, Louisiana and North Carolina — all captured by the GOP's presidential nominee, Mitt Romney, in 2012.

Louisiana Sen. Mary Landrieu and North Carolina Sen. Kay Hagan, both Democrats, each outraised the leading Republican candidates vying to replace them. Hagan took in $2 million in the final fundraising quarter of 2013, swamping the $700,000 collected by North Carolina House Speaker Thom Tillis, who hopes to be the GOP candidate facing her in November.

For her part, Landrieu opened the election year with $6.4 million in available spending money, exceeding Republican Rep. Bill Cassidy's $4.2 million stockpile of cash.

"In large part, we are winning the money race all over the country," said Justin Barasky, a spokesman for the Democratic Senatorial Campaign Committee. "It shows a rejection of voters, even in red states, of the recklessness of the Republican agenda. Voters don't want to re-litigate the health care law."

Sen. Mark Begich, D-Alaska, raised $850,000. But in an early sign of fundraising strength, Republican Dan Sullivan raised more than $1.2 million in the first three months of his candidacy, giving the state's former natural resources commissioner a big advantage in a three-way GOP primary. He joined the race last fall.

To bolster their prospects of retaining the Senate, Democrats have trained their sights on two Republican-held seats in the South. In one, Georgia Democrat Michelle Nunn, the daughter of former Sen. Sam Nunn, has been a fundraising powerhouse, collecting $1.6 million during the last three months of the year. A crowded field of Republicans is vying for the chance to face Nunn in November.

In the marquee race of the midterms, meanwhile, Kentucky Democrat Alison Lundergan Grimes matched the $2 million haul of Sen. Mitch McConnell, the Senate's top Republican. McConnell, a five-term incumbent, has a huge stockpile of unspent cash — $10.9 million, more than three times what Grimes has. But he also faces a primary opponent, Matt Bevin, while Grimes has clear shot to her party's nomination.

Bevin and other Tea Party-aligned candidates could complicate Republicans' election efforts. Six GOP incumbents — in Mississippi, Kentucky, South Carolina, Tennessee, Texas and Kansas — face primary opponents. Increasingly well-funded insurgent groups, such as the Tea Party Patriots and the Senate Conservatives Fund, plan to put their financial and organizational muscle behind several of the GOP upstarts.

In South Carolina, for instance, Sen. Lindsey Graham is headed into a June primary with four other GOP candidates. Tea Party-aligned groups have questioned his conservative credentials, citing his work on an immigration bill that would allow a path to U.S. citizenship for 11 million undocumented immigrants and his votes for Obama's Supreme Court nominees.

Graham is taking no chances. He raised $1.3 million in the final months of the year and started 2014 with more than $7.6 million in the bank — the largest campaign stockpile of his two-term Senate career.